The present invention relates to roadway grade measurements, and more particularly to apparatus for facilitating grade measurements between opposite roadway curb structures.
Roadway engineers generally reference all finish street grades to a datum that extends between opposite top of curb (TC) elevations. For contractors or inspectors to accurately determine the proper elevation and/or thickness of the required structural section or sections, a horizontal control is typically provided by holding a string line from one TC to the other on the opposite side of the street, from which a vertical depth or elevation can be measured by using a surveyor's rod or measuring tape. A disadvantage with this procedure is that two people are required for holding the opposite ends of the line, in addition to those that are required for measuring and recording the grade elevations. A device for referencing the grades of ditches is disclosed in U.S. Pat. No. 433,697 to Reichenbach, the device having a pair of stakes for driving into the ground, one of the stakes having an anchor for a string line, the other stake having a ratchet reel for storing and tensioning the line, the anchor and the ratchet reel being vertically adjustable on the respective stakes. This device is unsuitable for roadway grade measurements under many commonly encountered adverse conditions, such as rocky soil, a sidewalk located immediately adjacent to one or both curbs, buried utility lines, pipes and/or conduit, a datum that is located remote from the ground (such as where there are walls, barrier-type curbs, etc.), and existing trenches behind the curb and/or other obstacles that would reduce the work area.
It is also known to improvise a "curb hook" having a string attached. The hook would be engaged with one curb, with one man on the other curb to hold the string line taut against that curb. Thus it was possible to reduce the size of the crew by one.
However, even with the improvised curb hook, there remain significant problems; for example:
1. at least one crew member is required for locating and tensioning the string line, in addition to the one actually taking measurements;
2. existing curb hooks are ineffective in that they are not applicable to commonly encountered curb variations; and
3. existing curb hooks are unreliable in that they are subject to inadvertent disengagement because they are unstable, and because they are easily stretched out of shape under the moderate to high string line tension needed when measuring relatively wide roadways.
Thus there is a need for an apparatus for facilitating roadway grade measurements between opposing curbs that is reliable and effective with commonly encountered curb variations and roadway widths, that does not rely on the driving of stakes into the ground, and that is both easy and inexpensive to use.